Water-soluble quantum dots (QDs) have attracted much attention because of their excellent optical stability and biocompatibility. Here we report a simple, easy to operate, safe, and nontoxic method to synthesize water-soluble Ag₂S QDs and AgInS₂ (AIS) QDs. By addition of l-cysteine to the Ag⁺ and In³⁺ precursor solution, the water-soluble Ag₂S and AIS QDs can be synthesized through the hydrothermal method. With increased reaction temperatures and times, Ag₂S QDs were converted to AIS QDs. The colors were adjusted from green light to red light under UV light. The absorption spectra were red-shifted as a whole with increasing time and temperature. The fluorescence peaks at 80 and 90 °C did not change with time (greater or equal to 2 h), but the fluorescence peaks at 100 °C had a relatively large change from 470 to 650 nm. The band gaps of Ag₂S QDs had a large change from 2.2 to 0.9 eV due to crystallinity, and the band gap of the AIS QDs was about 0.9 eV. The photocatalytic H₂ production performance was studied. The results indicated that the Ag₂S QDs obtained by reaction at 90 °C for 4 h exhibited the greatest amount of H₂ production (1240 μmol·g^–1·h^–1). Finally, the reaction process was also investigated.

中文翻译：

---

从Ag ₂ S和AgInS ₂ QD一步合成水溶性量子点

水溶性量子点（QD）由于其出色的光学稳定性和生物相容性而备受关注。在这里，我们报告了一种简单，易于操作，安全且无毒的方法来合成水溶性Ag ₂ S QD和AgInS ₂（AIS）QD。通过将1-半胱氨酸添加到Ag ⁺和In ³⁺前体溶液中，可以通过水热法合成水溶性Ag ₂ S和AIS QD。随着反应温度和时间的增加，Ag ₂S QD已转换为AIS QD。在紫外光下将颜色从绿色调整为红色。随着时间和温度的增加，吸收光谱整体发生红移。80和90°C的荧光峰没有随时间变化（大于或等于2 h），但100°C的荧光峰在470 nm至650 nm之间有较大变化。由于结晶度，Ag ₂ S QD的带隙从2.2到0.9 eV有很大的变化，AIS QD的带隙约为0.9 eV。研究了光催化H _2的生产性能。结果表明，在90°C下反应4 h得到的Ag ₂ S QD表现出最大的H ₂产生量（1240μmol·g ^–1 ·h^–1）。最后，还研究了反应过程。